An SPR-Based Screening Method for Agonist Selectivity for Insulin Signaling Pathways Based on the Binding of Phosphotyrosine to Its Specific Binding Protein

A new screening method was developed that evaluates physiologically relevant chemical selectivity of agonists for insulin-signaling pathways. Phosphorylation (pY939) by an insulin-activated insulin receptor of a target peptide (Y939) derived from an insulin receptor substrate-1 (IRS-1) and its subsequent binding to another downstream target, the SH2 domain of PI-3 kinase (SH2N), were detected by surface plasmon resonance (SPR) spectrometry. This method is based on competitive binding of SH2N to pY939 either in a solution or on the gold surface of the SPR sensor chip. With increasing the concentration of pY939 in solution by the insulin-induced kinase reaction of insulin receptor, SH2N bound to pY939 in solution increases and the one on the sensor chip decreases, thereby causing a decrease in the SPR signal. The amount of thus-detected complex pY939−SH2N was found to depend on added insulin concentrations, confirming that the method utilized part of the sequential transduction mechanism of the insulin-sign...